In recent years, with the progress of portability enhancement of electronic devices, the use amount of secondary batteries is rapidly increasing. Application of secondary batteries spreads over not only devices with small electricity consumption such as cellular mobile phones and portable audio players but also equipment that requires high output power such as electric tools, electric motor-assisted bicycles and electric automobiles, and attention is focused on lithium ion batteries, which are capable of obtaining high energy density. Due to the increased application of lithium ion batteries to high output power devices, the necessity to recover valuable materials from spent batteries increases, and there are various techniques proposed for recovering valuable metals from lithium ion batteries.
For instance, in Non Patent Literature 1 (the first prior art), special features on recycling technologies of lithium ion batteries are reported, and methods for recovering valuable metals constituting lithium ion batteries are systematically described. According to a typical recycling method described in Non Patent Literature 1, for example, after mechanical processings such as opening, disassembling and grinding of spent lithium ion batteries, valuable metals in the batteries are dissolved by acid leaching, and then the desired constituents are each separately precipitated using a difference in solubility properties of the constituents, or desired valuable metals are each separately recovered by a treatment that desired constituents are preferentially extracted with solvents, or the like.
Further, in Patent Literature 1 (the second prior art), there is disclosed a technique where Cu and Co are recovered by using electrolysis with diaphragm in which a liquid containing dissolved valuable metals obtained by acid leaching is used as a catholyte, and a cation exchange membrane is used as a diaphragm.
Patent Literature
    Patent Literature 1: Japanese Patent No. 3675392Non Patent Literature    Non Patent Literature 1: Jinqiu Xu et al., “A review of processes and technologies for the recycling of lithium-ion secondary batteries”, Journal of Power Sources, vol. 177, pp. 512